The Advanced Configuration and Power Interface (ACPI) specification is an open standard for power management. The ACPI specification defines system states and component states for a computing system. The system states in ACPI are G0 (S0) operating, G1 Sleeping, which can be divided into sleep system states S1 through S4, G2 (S5) Soft Off and G3 Mechanical off. In G2 some components can remain powered so the computing system can go to G0 from an input of the power button, modem, LAN, or real time clock (RTC) alarm.